Better Beer from Genetically Engineered Yeast

PopMech talks to Kevin Verstrepen, a leading yeast geneticist at the Flanders Institute for Biotechnology and the University of Leuven, Belgium, and Troels Prahl, the head of research and development at the Southern California yeast repository White Labs, to find out why.

In genetics laboratories worldwide, brewing yeast—the microorganisms that transmute tepid grain water into tasty beer—have been genetically engineered to brew stranger and more flavorful brews than anything you can find on the shelf. However, as genetically engineered yeast has become easier and easier to create, a slew of ethical, legal, and marketing issues have kept these futuristic brewing yeasts from leaping out of the laboratory and into the brewery. We wanted to find out why.

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The Power of Yeast

Yeast plays a crucial role in the beer-brewing process. Organisms that exist in stunning diversity around the world, they can produce more than 500 flavor and aroma molecules, according to Troels Prahl, the head of research and development at the Southern California yeast repository White Labs. And in most beers, yeast can account for up to a third of a brew's final flavor.

Each variety of brewing yeast has its own genetic limitations, though. Some can produce great-tasting beer, but only under hard-to-manage conditions. Others make beer too cloudy, not alcoholic enough, or create small off-tastes.

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But almost more than any other organism, brewing yeast is at the forefront of genetic research and synthetic biology (credit a historical tie between brewing and microbiology.) Thanks to yeast projects that have pushed the boundaries of genetic engineering, and ongoing, decades-long work to understand the yeast genome, our ability to tailor the DNA of brewing yeast has grown exponentially.

Today, geneticists have not only mastered the ability to make drastic tweaks in a yeast's genetic code—for example, chopping out the gene that creates the butter-flavored molecule diacetyl that tastes disgusting in beer, or turning up the volume on genes behind alcohol tolerance and the tasty banana and clove flavors made by hefeweizen yeasts—but may soon have the ability to redesign and custom-tailor the genome. With this genetic power, a brewer would be able to choose from the enormous range of yeast-produced factors (flavor, clarity, mouth feel, alcohol tolerance, and aroma) and then have a yeast genetically engineered to match.

Backlash Fears

Kevin Verstrepen, a leading yeast geneticist at the Flanders Institute for Biotechnology and the University of Leuven, Belgium, notes that today there is not a single commercial beer on the market that is made with genetically engineered yeast. But, he says, the U.S. Food and Drug Administration (and its European counterpart) have clear pathways to bring these yeasts to the market. In fact, some American wines are already being made with a genetically modified wine yeast, called ML01—it lacks the genes that produce a chemical that gives some wine drinkers headaches. This genetically modified yeast does not have to be identified on wine labels.

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The biggest hurdles for these new yeasts probably won't be legal ones but marketing. Public wariness of genetically engineered foodstuffs, warranted or not, has bred a resistance in large breweries—the only beer producers with the funds to gain FDA approval. Regardless how they may feel about the yeasts or the new beers they could be brewing, those brewing companies want nothing to do with a negative PR backlash.

Jan Steensels, a microbiologist with Verstrepen's lab, summed up the situation for The New York Times: "Right now we have a few hundred genetically modified yeast strains patiently waiting in our laboratory's freezer." And because of the negative PR worry, "most brewers don't want anything to do with them."

Risk Factors?

Fears about genetically modified food products—beer yeast included—could be more or less divided into two distinct issues: first, that the yeasts will somehow unintentionally harm the consumer's health, and second, that if the yeasts escape the laboratory or brewing facility, they could harm the surrounding ecosystem or population of wild yeasts.

Considering a potential negative health impact, Prahl and Verstrepen both agree that this concern is almost entirely unfounded. For one, yeast, unlike genetically modified foods such as corn or meat, is not designed to be consumed. "So if you're using one of these yeasts to make filtered beer," Prahl says (and almost all commercial beers are filtered), "then there'd be no genetically modified yeast or yeast DNA in the final beer for anyone to consume anyhow."

Even if the yeast were to be consumed, for argument's sake, Verstrepen notes that a large number of genetic techniques currently in use, which encompass things such as deleting small chunks of genetic data or swapping in genes from a closely related yeast strain—don't involve introducing novel genes into the organism that would make health-harming compounds. Nor do the current genetic techniques require leaving any molecular markers or tools behind in the DNA.

"Even hypothetical risks—like accidentally introducing an allergen, for example—are all things you test for before you have your yeast strain approved and legalized," Verstrepen says. "As for the general public being afraid that these [genetically engineered] yeasts will produce something like cancer or some horrible disease—that is totally bogus."

The ecological concern is more nuanced, Verstrepen says. Here, his main concern is the prospect of introducing non-yeast genes into a yeast, with the worry that these new, human-picked genes could be bred or passed on across yeasts in the outside world. "And this is a serious concern. You need to understand what you're doing, and make sure you're not going to accidentally confer some ecological advantage to the outside population," he says.

Even if these new yeasts were to escape, he explains, the chances of them out-competing other, wild yeast species—given that beer yeast is tailored to perform in a very unnatural environment—is unlikely, but certainly worth watching for.

A Delay's Silver Lining

Prahl says he thinks public opinion on genetic engineering may be shifting, "and I feel like it might be time to revisit this issue to figure out if the public resistance is just perceived by the brewers, or if it's real," he says. Both he and Verstrepen independently mentioned that many small craft brewers would have no issue making use of genetically engineered yeasts if they were available.

Still, Verstrepen sees a silver lining to the breweries' resistance to adopt these new yeasts. "It's not necessarily a bad thing that we're moving slower with the application of these [engineered] yeasts than we are with the development," he says. "As times goes by, our technology is only getting better, and we're learning more and more about what we're doing and the potential impacts of these organisms."

Prahl says that an increased genetic understanding of brewing yeast will increase our ability to naturally breed yeasts in smarter and more efficient ways.

"Personally, I'm a believer in doing things as naturally as possible and not messing with the genome unless it's absolutely necessary," he says. "But it depends on what we stand to gain. As long as there's a greater cause, and an informed dialogue, we should be open to these technologies."